The present invention relates to the stabilization of projectiles in flight.
The invention more particularly relates to the aerodynamic stabilization of projectiles of a type that, during flight, are designed to jettison either a forward or an aft body that was connected to the projectile when it was initially launched, as from a gun or a missile. Those skilled in the art are well aware of the context or contexts in which such a mode of operation occurs.
Aerodynamic stabilization of a projectile in flight, i.e., preventing it from tumbling, is achieved by making the center of the lifting forces, also referred to as the center of pressure, lie behind the center of mass. The distance between these centers and divided by the total projectile length is called the static margin. Even if the projectile is stable when launched, its static margin may sufficiently change after the body that was attached to it is jettisoned that the static margin is no longer sufficient to ensure stable flight.
Reference is made to our co-pending and commonly-assigned U.S. patent application Ser. No. 10/396,222, filed of even date herewith, entitled, xe2x80x9cAerodynamic Stabilization of a Projectile,xe2x80x9d and hereby incorporated herein by reference. In accordance with the invention set forth in that patent application, the lift force center, or center of pressure, of a projectile is caused to move upon the occurrence of an event that changes the static margin, such as the jettisoning of a body previously attached to the projectile. This is illustratively achieved by a flare disposed toward the rear of the projectile. The flare has elements that deploy from a first, stowed position to a second, deployed position upon the occurrence of the jettisoning, or separation, event. In the stowed position, the deployable elements are aligned with the air stream, in order to minimize drag. In the deployed position, the deployable elements project into the air stream in such a way as to move the lift center rearward. Deployment of the deployable elements is illustratively achieved by taking advantage of an abrupt change in velocity (i.e., an acceleration or deceleration) that occurs when the attached body and the projectile are separated from one another by, for example, the setting off of a propellant charge that drives them apart while in flight. An inertial component of the flare, illustratively a slide ring, is arranged to shift position relative to the rest of the flare in response to the abrupt velocity change and is connected to the deployable elements in such a way, and has sufficient inertia, as to move the deployable elements to their deployed positions upon separation. A detent mechanism is provided to lock the deployable elements in place once they have been moved to their deployed position. This is illustratively achieved by locking the aforementioned inertial component in its displaced position. The deployable elements comprise a number of petals each hinged at one end to a support ring and arrayed around a central axis of the flare. The inertial component is, as previously mentioned, illustratively a slide ring to which each petal is linked in such a way that the displacement of the slide ring swings the petals around their hinged ends to their deployed positions. The projectile launch acceleration may be on the order of four times as large as the separation acceleration. In order to prevent the aforementioned inertial component from prematurely deploying the deployable elements during the launch acceleration of the projectile, the flare illustratively includes a plurality of slide supports, supported by a retaining element, thereby keeping the shifting element and the deployable elements in their original positions. The retaining element also engages with the deployable elements to preclude any fluttering in flight that might occur while they are in their stowed position. The retaining element detaches from the rest of the flare at the separation event, thereby allowing the deployable elements to deploy under the influence of the inertial component.
The present invention is directed to an embodiment of the invention set forth in the above-cited patent application.
In accordance with a feature of the invention the aforementioned detent mechanism is illustratively a set of fingers, or detents, whose position is fixed relative to the support member. Each detent rests on a respective protrusion on the outside of the slide ring. When the slide ring shifts to its displaced position, the protrusions are pulled out from under their respective detents. The detents are biased inwardly and so slip into place behind their respective protrusions, thus locking the slide ring in place, preventing it from returning to its original position, and thereby maintaining the petals in their outwardly swung position.
There are illustratively six of the aforementioned slide supports in the form of a right pentagonal prism wedged between the slide ring and the retaining element. When the retaining element detaches from the rest of the flare, the slide supports simply fall away. The retaining element itself illustratively comprises a segmented ring made up of six wedges, or ring segments. A lip on one side of each ring braces against the aft body and a lip on the other side of each ring segment engages a respective one of the petals so as to prevent any possible fluttering of the petal during flight, as already mentioned. The ring segments are held in place by being wedged between the ail body and the projectile but are not permanently affixed to either of them. They simply fall away when the aft body and projectile separate.
The embodiment to which the present invention is directed has six of the aforesaid petals.
A different embodiment of a flare embodying the principles of the invention is the subject matter of co-pending and commonly-assigned U.S. patent application Ser. No. 10/396,220 filed of even date herewith entitled, xe2x80x9cDeployable Flare With Simplified Design,xe2x80x9d the applicants of that patent application being John Daryl Carlyle, William Leroy Hall, Hartley Hughes King, Thomas Louis Menna, Lawrence Steven Romero. That application is also hereby incorporated herein by reference.